The present invention is directed to an engineered wood member and to its method of manufacture. The members are particularly useful as studs for building construction.
Even after hundreds of years, wood framing remains the method of choice for building construction in the United States and many other parts of the world. However, the forest economy has within the past two decades turned from an emphasis on harvesting huge old growth trees to much smaller plantation grown trees. Much of this plantation stock has been grown from genetically improved seedlings selected for rapid growth, high density, and many other desirable heritable characteristics. Along with the change in the nature and size of logs, sawmilling has also evolved into mills that can rapidly process the smaller trees into lumber. Many mills now use chipper-canters which first convert wood along the sides of the logs into pulp chips and leave a cant with parallel sides of a predetermined width. If the log was sufficiently large, side boards may be taken off the initial cant leaving a center cant to be cut into additional boards, usually in an automated gang saw. Scanners are widely used to measure the logs and set the saws to determine the breakdown pattern. Larger logs will yield side boards and a center cant. In order to maximize yield, wane will often be allowed along the corners of some pieces. Wane results from the piece not entirely fitting into a prescribed cross sectional rectangle for all or part of its length so that some of the original surface adjacent to the bark remains along one or more edges. Grading rules permit minor wane for most lumber grades but excessive wane is cause for downgrading or rejection of an individual piece.
Wane and other edge defects on lumber are particularly annoying to builders. Wall studs may be taken as an example. These have other materials nailed to them including sheathing and siding on the exterior and gypsum drywall on the interior. For ease of nailing and solidity of construction a sound, full width flat surface is desirable.
Coniferous trees have a core portion of juvenile wood about 10-15 growth rings wide. This core wood is known to be less dense and generally weaker than wood formed later during the trees growth. It is inherent that lumber having wane will have come from the outside portion of the log from which it was cut and will generally be of higher strength and stiffness than that cut from the core portion of the log. If the trees have been pruned during their growth, lumber from the outside will also usually have a lower amount of defects such as knots. For these reasons it is desirable to convert this wood into the highest value product possible. Removing any wane without substantial loss in yield would be a major step in increasing lumber value since the affected lumber generally has prime structural characteristics.
The present invention offers a solution to the problems caused by wane and presents a premium product that is wane free and full sized. The product can be made by upgrading pieces having moderate wane without loss in lumber dimensions.
The present invention is directed to an engineered wood construction member of rectangular cross section having flat edges free of wane, manufacturing damage, and other surface defects. The invention is further directed to the method of manufacture of the product. The wood member is particularly useful as studs for wall framing but not so limited. The member is formed from two side-by-side opposed wood strips. The upper and lower a corners of the adjacent faces of the strips have been cut away to form rectangular notches running the full length of the strips. Wood-like splines affixed top and bottom into the notches join them into a unitary member.
The process for making the members is carried out in a sequence of steps. A lumber piece having wane along one or more edges is first milled to produce rectangular notches along each of the four corners. The piece is then sawn lengthwise through the shorter of the cross sectional dimensions. Each resulting strip is then turned or rotated 180xc2x0 and the strips are placed side-by-side so that the notched corners are adjacent to each other and, in essence, form longitudinal channels. A wood-like material is then fitted into the channels formed by the notches and solidly attached in place as by adhesive bonding, stapling, nailing or other mechanical means to again form the two strips into a unitary member. The two sides and/or the faces may optionally be lightly planed or sanded to produce smooth surfaces. The strips may be in contact with each other or they may be placed slightly apart; e.g. up to about 1-75 mm, in the finished member. Some of the lumber width will be lost to saw kerf when the piece is ripped lengthwise. By including a small space between the strips the dimensions of the original lumber piece may be restored. Using the wider spacing, a nominal 2xc3x974 board can be expanded into a 2xc3x976.
The splines may be made of wood or a reconstituted wood product such as oriented strand board. Other materials of a wood-like nature may also be used such as hardboard, or particleboard. The term xe2x80x9cwood-likexe2x80x9d should be construed sufficiently broadly to include any material of sufficient structural strength and rigidity that can be readily attached and worked with conventional wood working tools. Oriented strand board adhesively bonded into the channels is preferred.